Rotary engines, such as for example Wankel engines, use the rotation of a piston to convert pressure into a rotating motion, instead of using reciprocating pistons. In these engines, the rotor typically includes a number of seals that remain in contact with a peripheral wall of the internal cavity of the engine throughout the rotational motion of the rotor to create a plurality of rotating chambers when the rotor rotates.
Rotary engines come in many forms. One well-known type, the Wankel engine, has a generally triangular rotor received in a two-lobed epitrochoid cavity. Other non-Wankel rotary engines types exist as well.
Rotors and internal cavities of rotary engines may be difficult to inspect, often requiring substantial disassembly to be able to inspect the more critical regions where combustion occurs.